In known generator systems for converting thermal energy to electric energy there is provided a magnetic circuit of a suitable magnetic material and a coil arranged around the magnetic circuit. A temperature-varying arrangement varies the temperature of the magnetic circuit alternately above and below a phase transition temperature such as the Curie point to thereby vary the reluctance of the magnetic circuit and the resulting magnetization of the magnetic circuit is modulated by the varying reluctance so as to induce electric energy in the coil arranged around the magnetic circuit. The temperature-varying arrangement passes alternately hot and cold fluid by the magnetic circuit and comprises typically one or several feed pumps, piping, and a valve manifold.
JP 7107764 discloses such generator system provided with a switch valve comprising a hot water inlet port, a cold water inlet port, and outlet pipes. When the switch valve rotates the outlet pipes receive alternately water from the hot water inlet port and the cold water inlet port. The phase between the outlet pipes is 180°.